This invention relates to magnetic tape cassettes, and more specifically to structures of magnetic tape cassettes.
Ordinarily, magnetic tape cassettes have tape kind detecting openings formed in the rear portion. In the injection molding of tape cassettes, therefore, it is necessary to use specially designed molds to produce cassettes suited for the individual types of tapes to be contained, adding to the cost of manufacture. In an effort to overcome this difficulty, we previously devised a magnetic tape cassette which, as illustrated in FIGS. 11 and 12, has a rear portion of the cassette housing as an independent rear frame member 8 separable from the main body 10. The device is covered by our copending U.S. Pat. No. 4,892,266, said application being incorporated by reference into the present application.
The construction of the magnetic tape cassette disclosed in the above patent application is effective in reducing the manufacturing cost in job-shop type production. However, the recent tendency is toward diversification of the structural material to impart more varied colors, feels, and textures to magnetic tape cassettes. For example, we previously advocated the adoption of a double-layer structure for the upper and lower half housing sections that contain tape-holding components of a cassette, in our copending U.S Pat. No. 4,965,690 which application is incorporated by reference into the present application.
If the outside layer of the double-layer structure is made of a material with a high coefficient of friction, such as n elastomer, the side portions of the resulting magnetic tape cassette that come in direct contact with the holder of a recording-reproducing device when the cassette is loaded into the device naturally have surfaces of the same high-friction-coefficient material. This can reduce the smoothness with which the tape cassette is taken out and impair the rigidity of the cassette itself, adversely affecting the dimensional accuracy of its half housing sections. For this reason the trend to changes in structural material has its limitations.
Another magnetic tape cassette of the prior art has upper and lower half housing sections of double-layer structure made by two-color molding, each section consisting of an inside layer of a rigid material and a relatively flexible, high-friction coefficient outside layer such as of an elastomer, As shown in FIG. 10, the both housing section are molded with the outside layers 3 simply fitted in corresponding recesses 5 formed in the inside layers 1. Consequently, fins 3' left by pouring gates (not shown) used in molding the outside layers and also formed of the outside layer material are exposed, marring the appearance of the resulting cassette. Furthermore, because the outside layer are joined to the inside layers merely by bonding force, they tend to come off easily upon subjection to forces exerted on the surface.
In two-color molding, it is common that, as shown in FIGS. 30 and 30A, and primary molding side of the interface between the inside layer 1 and the outside layer 3, i.e., the outer surface of the inside layer 1, has a satin crape finish 5, whereas the outer surface of the outside layer 3 has a mirror finish 7. This interfacial structure is designed for increased bond strength through more intimate engagement of the inside and outside layers 1, 3. Nevertheless, the structure sometimes causes the outside layer 3 to come off partly from the inside layer 1, as indicated by an arrow a in FIG. 30, at the time the half housing section is taken out, following the injection molding of the outside layer 3, from the outside layer-forming mold (not shown). The peeling is ascribable to the fact that the interfacial adherence of the interface between the mirror surface 7 and the corresponding surface of the mold is greater than that of the satin crape interface between the inside and outside layers. The only step thus far taken to preclude the phenomenon has been, as illustrated in FIGS. 31 and 31A for reference, to mirror finish the outer surface 9 of the inside layer to increase the interfacial adherence between the inside and outside layers. The outer surface of the outside layer is left mirror smooth as indicated at 11. With the interfacial adherence between the mating surfaces of the mold and the outside layer, no such countermeasure as above has been taken to prevent the partial separation of the inside and outside layers.
Still another magnetic tape cassette of the prior art, as indicated in FIGS. 37, 38, and 39, have a pair of hub openings 19 formed through the upper and lower half housing sections. At least one of the two housing sections has a tape-view window member 15 formed generally in the center. In so-called two-color molding whereby the upper and lower half housing sections are made of a double-layer structure, it has been customary, as shown in FIG. 38, to form each hub opening 19, inclusive of the surrounding tapered rim 21, solely of the inside layer 1. The outside layer 3 is so formed as to surround an annular raised rim 13 of the inside layer 1. Structurally, the same applies to the window. As FIG. 39 shows, the inside layer 1 is raised as at 17 to surround the window member 15, e.g., of clear plastic material, and the outside layer 3 is so formed as to surround the raised rim 17. The structure is required to prevent the peeling of the outside layer 3 from around the window member upon application of external forces. The structure naturally exposes a large area of the inside layer 1 to the surface of the cassette as viewed in FIG. 37. If, for example, the outside layer 3 is satin crape finished, its design integrity with the outside layer material is impaired. The structure thus has its limitation in respect of design.
Therefore, it is an object of the present invention to provide a magnetic tape cassette with high flexibility in changing color, feel and texture with different structural materials for the fabrication of upper and lower half housing sections thereof.
Another object of the invention is to provide a magnetic tape cassette which ensures smooth releasability from recording-reproducing devices in which it is loaded, irrespective of the structural materials used in upper and lower half housing sections.
Another object of the invention is to provide a magnetic tape cassette capable of maintaining high rigidity of half housing sections regardless of the structural materials used in the sections.
Still another object of the invention is to provide a magnetic tape cassette having separable side frame members of a low coefficient of friction.
Yet another object of the invention is to provide a magnetic tape cassette in which the remains of pouring gates and fins formed at the time of molding of the outside layer material are not exposed on the outer surface of the outside layer in each of upper and lower half housing sections having a double layer structure of inside and outside layers.
A further object of the invention is to provide a magnetic tape cassette having upper and lower half housing sections of a double-layer structure consisting of inside and outside layers, in which the outside layer is difficult to peel off from the inside layer.
Still a further object of the invention is to facilitate assembling of a magnetic tape cassette by providing mutually engageable, temporary fastening means at points where side frame members and main body are joined using tapping screws.
An even further object of the invention is to further facilitate assembling of a magnetic tape cassette by providing mutually engageable, temporary fastening means not only at points where side frame members and main body are joined by tapping screws but also at points where the side frame members and a rear frame member are joined likewise.
An additional object of the invention is to eliminate the possibility of inside and outside layer separation along the interface at the time of release from the mold, by reducing the interfacial adherence between the mating surfaces of the outside layer-forming mold and the outside layer.
Another additional object of the invention is to provide a magnetic tape cassette in which, even if half housing sections thereof have a double-layer structure, the exposed portions of the inside layer around hub openings and tape-view windows are made inconspicuous lest it mar the design integrity of the outside layer material.